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Author Topic:   Coosa Material for Bench-style Seats

RickCFL posted 05-02-2014 09:43 AM ET (US)
I hear COOSA material is more rigid than starboard. [I am] trying to make bench-style seats on my 16-footer. The distance is approx. 63.5-inch across, so I know I would need a support or two to hold it up. Do readers have experience with COOSA material?
fishgutz posted 05-02-2014 10:04 AM ET (US)
Looks interesting. Not pretty, though.
http://www.coosacomposites.com/index.htm
RickCFL posted 05-02-2014 10:06 AM ET (US)
Apparently you can either glass over it or also paint to finish. I am doing Interlux perfection on rest of the boat so it could be used here as well. Then add cushion for seating.
Binkster posted 05-02-2014 12:33 PM ET (US)
I think it is meant to be used as a decking material, not for what you are looking for, and like Divinycell, I'm sure it is very expensive. Why not use Sapele mahogany. It is available in a specialty lumber yard in Homosassa for about $5.50 a board foot. You need a 6ft X 12" wide by 5/4 " thick board, which is about 8 bd ft, per seat. that comes to $44 per seat and he will plane the boards smooth and cut them to length for a couple of dollars more. Then just brush on 5 coats of varnish and you are ready to go.

rich
DVollrath posted 05-02-2014 01:30 PM ET (US)
I used Coosa for the console floor of my Montauk, replacing the deteriorated plywood original. It works fine for that, but as others have mentioned it is not cheap and has a very rough unfinished surface. I gel-coated mine, more as a way to practice gel coating than any good reason.
I don't think it is an appropriate material for a seat. Like Rich said, it's more of a deck or console substrate. I also agree that Sapele or some other appropriate wood would be a better choice for your application.
Dennis
RickCFL posted 05-02-2014 02:25 PM ET (US)
I certainly like the $50 price range. Trying to stay away from wood for weight ~~issues~~, but to use mahogany and then paint white over it seems a shame. I wnat the seats to stay white. Any other material that you can think of to make seats?
DVollrath posted 05-02-2014 03:10 PM ET (US)
Rick--if you want white matching your interior, then perhaps the easiest way to go is to use a marine plywood core and paint it. Plywood 3/4-inch is around 61-lbs [er sheet or 1.9-lbs/sqquare-foot. If you use 8-square-feet for bench and supports, you would have about 15.25 pounds of core. The lightest Coosa in 3/4-inch is about 1.25-lbs/square-foot, so you'd save only 5-lbs. Wood is one of the strongest building materials per pound in common use.
It's all personal aesthetics, but I really like the look of wood accents on a fiberglass boat.
Dennis
RickCFL posted 05-02-2014 03:16 PM ET (US)
Thank you, Dennis. I will google where to find marine plywood in my area.
Binkster posted 05-03-2014 04:31 PM ET (US)
The only difference between marine plywood and exterior fir plywood, is that marine plywood doesn't have any voids in the inner ply, both use the same glue, and are fir plywood. Voids in the inner ply isn't desireable for hull sides, but is not a problem for seats. A seat cut from 3/4-inch plywood has a big sag factor, unless you build a frame under it and you also must cover the end grains with wood. Now you have a carpentry project. Home Depot or Lowes sells pine not fir plywood. Their hardwood plywood is interior, not suitable for boats. You need to find a real lumberyard.
rich
dfmcintyre posted 05-03-2014 07:16 PM ET (US)
Rick--I think the first choice is deciding either on plywood that you paint, or mahogany that you coat with clear.
Regards - Don
wezie posted 05-04-2014 01:03 PM ET (US)
If you paint mahogany, the real wood will always be there protected by paint. That may be the best weight and dollar decision. Buy only what you need. Good Luck!
contender posted 05-04-2014 02:03 PM ET (US)
I would do what Bink states about the sapele mahogany.
RickCFL posted 05-05-2014 10:35 AM ET (US)
Thanks all!
RickCFL posted 05-05-2014 12:12 PM ET (US)
Ok. New info received from my local fiberglass company that has been very helpful with my project. They sell nida core 4'x8' sheets that he is saying I can use for my bench seats. Glass them over with matt and resin; cut to size etc.. Supports to hold up for my 63" span. Light weight and only $70 a sheet plus matt and resin. I can make 2 bench seats from one sheet. Anyone have experience with this nida core product?
dfmcintyre posted 05-05-2014 01:45 PM ET (US)
Yes.
Worked with another guy, and we fabricated, glassed and painted the replacement gate for the Mount Hope Cemetery in Lansing, Michigan. Honest! It's held up well. Link to an image on Facebook:
https://www.facebook.com/LansingCemeteries
It's essentially a honeycombed all plastic material.

1/2 or 3/4", and glassed covered or scrim sheet covered? I'd lean towards 3/4". If scrim sheeted, paint on a coating of resin prior to laying down glass, otherwise the scrim can soak up the resin meant for the glass. If using epoxy resin, use a slow cure resin for the initial coating, you run a slight risk of warping when the resin kicks and starts to heat.
For the type of glass, I'd go roving on the bottom (no one is going to see it...) followed by 1.5oz mat on the bottom, maybe two layers on the top. Seal the edges and your good to go for painting. If you laminate two pieces together for supports, it will be totally non-rotting.
Regards - Don
RickCFL posted 05-05-2014 02:49 PM ET (US)
Thanks Don!
RickCFL posted 05-06-2014 02:44 PM ET (US)
Don,
Doing just that. 3/4" nida core; Fiberglass guys helped me buy the resin, fiberglass sheets, putty for edges, hardener, etc.. Why not add to the time on this project; haha! Custom seats, non-rot, fit, light, affordable. All good things for me.
Wish I could post some darn pixs. 25hrs into it. 1st coat of Perfection this past weekend and it already looks done inside. 2nd coat this weekend; then moving to outside hull. In between will build the custom seats and side console.
Thanks all.
dfmcintyre posted 05-06-2014 09:23 PM ET (US)
Rick -
If you open or have an account in one of the photo hosting sites; Photobucket, Picasa, etc., you first post the images to that site, copy the address and paste in your message. Be sure to add at the beginning:
[url]
and at the end of the address:
[url]

That tells the hosting software that there's an embedded link.
Regards - Don
RickCFL posted 05-07-2014 02:20 PM ET (US)
http://s105.photobucket.com/upload
Does this work? Can you see pix?
jflots posted 05-13-2014 04:21 PM ET (US)
I used coosa for a stern seat in our 18 outrage because of weight. I built a starboard grid runs forward from the transom and over the motor well berm, so it hovers off the floor. The coosa panel runs the full beam in side the gunwale boards and has teak grates on either side of the engine behind it. We laid up nonskid area from a mold and cut them to fit, then gelled the perimeter and a slick in the center. The forward and aft edges are trimmed in teak. It turned out very nice and looks like it could be original. In hindsight I should have layered some more 'glass to help stiffen it. Coosa is soft and can flex if un supported.
Other than that it works great.
RickCFL posted 05-14-2014 10:21 AM ET (US)
Thanks. Have gone back to marine plywood 3/4 x 2 sheets from gunwale side to side; glassed over with matt/resin etc.. Probably need verticle supports but will deal with later.

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Author	Topic: Coosa Material for Bench-style Seats
RickCFL	posted 05-02-2014 09:43 AM ET (US) I hear COOSA material is more rigid than starboard. [I am] trying to make bench-style seats on my 16-footer. The distance is approx. 63.5-inch across, so I know I would need a support or two to hold it up. Do readers have experience with COOSA material?
fishgutz	posted 05-02-2014 10:04 AM ET (US) Looks interesting. Not pretty, though. http://www.coosacomposites.com/index.htm
RickCFL	posted 05-02-2014 10:06 AM ET (US) Apparently you can either glass over it or also paint to finish. I am doing Interlux perfection on rest of the boat so it could be used here as well. Then add cushion for seating.
Binkster	posted 05-02-2014 12:33 PM ET (US) I think it is meant to be used as a decking material, not for what you are looking for, and like Divinycell, I'm sure it is very expensive. Why not use Sapele mahogany. It is available in a specialty lumber yard in Homosassa for about $5.50 a board foot. You need a 6ft X 12" wide by 5/4 " thick board, which is about 8 bd ft, per seat. that comes to $44 per seat and he will plane the boards smooth and cut them to length for a couple of dollars more. Then just brush on 5 coats of varnish and you are ready to go. rich
DVollrath	posted 05-02-2014 01:30 PM ET (US) I used Coosa for the console floor of my Montauk, replacing the deteriorated plywood original. It works fine for that, but as others have mentioned it is not cheap and has a very rough unfinished surface. I gel-coated mine, more as a way to practice gel coating than any good reason. I don't think it is an appropriate material for a seat. Like Rich said, it's more of a deck or console substrate. I also agree that Sapele or some other appropriate wood would be a better choice for your application. Dennis
RickCFL	posted 05-02-2014 02:25 PM ET (US) I certainly like the $50 price range. Trying to stay away from wood for weight ~~issues~~, but to use mahogany and then paint white over it seems a shame. I wnat the seats to stay white. Any other material that you can think of to make seats?
DVollrath	posted 05-02-2014 03:10 PM ET (US) Rick--if you want white matching your interior, then perhaps the easiest way to go is to use a marine plywood core and paint it. Plywood 3/4-inch is around 61-lbs [er sheet or 1.9-lbs/sqquare-foot. If you use 8-square-feet for bench and supports, you would have about 15.25 pounds of core. The lightest Coosa in 3/4-inch is about 1.25-lbs/square-foot, so you'd save only 5-lbs. Wood is one of the strongest building materials per pound in common use. It's all personal aesthetics, but I really like the look of wood accents on a fiberglass boat. Dennis
RickCFL	posted 05-02-2014 03:16 PM ET (US) Thank you, Dennis. I will google where to find marine plywood in my area.
Binkster	posted 05-03-2014 04:31 PM ET (US) The only difference between marine plywood and exterior fir plywood, is that marine plywood doesn't have any voids in the inner ply, both use the same glue, and are fir plywood. Voids in the inner ply isn't desireable for hull sides, but is not a problem for seats. A seat cut from 3/4-inch plywood has a big sag factor, unless you build a frame under it and you also must cover the end grains with wood. Now you have a carpentry project. Home Depot or Lowes sells pine not fir plywood. Their hardwood plywood is interior, not suitable for boats. You need to find a real lumberyard. rich
dfmcintyre	posted 05-03-2014 07:16 PM ET (US) Rick--I think the first choice is deciding either on plywood that you paint, or mahogany that you coat with clear. Regards - Don
wezie	posted 05-04-2014 01:03 PM ET (US) If you paint mahogany, the real wood will always be there protected by paint. That may be the best weight and dollar decision. Buy only what you need. Good Luck!
contender	posted 05-04-2014 02:03 PM ET (US) I would do what Bink states about the sapele mahogany.
RickCFL	posted 05-05-2014 10:35 AM ET (US) Thanks all!
RickCFL	posted 05-05-2014 12:12 PM ET (US) Ok. New info received from my local fiberglass company that has been very helpful with my project. They sell nida core 4'x8' sheets that he is saying I can use for my bench seats. Glass them over with matt and resin; cut to size etc.. Supports to hold up for my 63" span. Light weight and only $70 a sheet plus matt and resin. I can make 2 bench seats from one sheet. Anyone have experience with this nida core product?
dfmcintyre	posted 05-05-2014 01:45 PM ET (US) Yes. Worked with another guy, and we fabricated, glassed and painted the replacement gate for the Mount Hope Cemetery in Lansing, Michigan. Honest! It's held up well. Link to an image on Facebook: https://www.facebook.com/LansingCemeteries It's essentially a honeycombed all plastic material. 1/2 or 3/4", and glassed covered or scrim sheet covered? I'd lean towards 3/4". If scrim sheeted, paint on a coating of resin prior to laying down glass, otherwise the scrim can soak up the resin meant for the glass. If using epoxy resin, use a slow cure resin for the initial coating, you run a slight risk of warping when the resin kicks and starts to heat. For the type of glass, I'd go roving on the bottom (no one is going to see it...) followed by 1.5oz mat on the bottom, maybe two layers on the top. Seal the edges and your good to go for painting. If you laminate two pieces together for supports, it will be totally non-rotting. Regards - Don
RickCFL	posted 05-05-2014 02:49 PM ET (US) Thanks Don!
RickCFL	posted 05-06-2014 02:44 PM ET (US) Don, Doing just that. 3/4" nida core; Fiberglass guys helped me buy the resin, fiberglass sheets, putty for edges, hardener, etc.. Why not add to the time on this project; haha! Custom seats, non-rot, fit, light, affordable. All good things for me. Wish I could post some darn pixs. 25hrs into it. 1st coat of Perfection this past weekend and it already looks done inside. 2nd coat this weekend; then moving to outside hull. In between will build the custom seats and side console. Thanks all.
dfmcintyre	posted 05-06-2014 09:23 PM ET (US) Rick - If you open or have an account in one of the photo hosting sites; Photobucket, Picasa, etc., you first post the images to that site, copy the address and paste in your message. Be sure to add at the beginning: [url] and at the end of the address: [url] That tells the hosting software that there's an embedded link. Regards - Don
RickCFL	posted 05-07-2014 02:20 PM ET (US) http://s105.photobucket.com/upload Does this work? Can you see pix?
jflots	posted 05-13-2014 04:21 PM ET (US) I used coosa for a stern seat in our 18 outrage because of weight. I built a starboard grid runs forward from the transom and over the motor well berm, so it hovers off the floor. The coosa panel runs the full beam in side the gunwale boards and has teak grates on either side of the engine behind it. We laid up nonskid area from a mold and cut them to fit, then gelled the perimeter and a slick in the center. The forward and aft edges are trimmed in teak. It turned out very nice and looks like it could be original. In hindsight I should have layered some more 'glass to help stiffen it. Coosa is soft and can flex if un supported. Other than that it works great.
RickCFL	posted 05-14-2014 10:21 AM ET (US) Thanks. Have gone back to marine plywood 3/4 x 2 sheets from gunwale side to side; glassed over with matt/resin etc.. Probably need verticle supports but will deal with later.